In wireless cellular systems such as, for example, the 3G Long Term Evolution (“3G LTE”), WiMAX and WCDMA systems, the nodes which control traffic to and from users in the cells of the systems, said nodes being referred to by various names in the various systems, for example “eNodeB” in LTE systems, can be equipped with multiple antennas for transmission and/or reception, and will thus be able to use various multi antenna transmission techniques. Examples of such techniques are transmit diversity, spatial multiplexing, and beam forming with dedicated reference signals. Such techniques may in fact become integral parts of the systems.
Accordingly, in the kind of systems mentioned above, there may be a variety of multi antenna transmission techniques or modes employed, which makes it important for all parties in a cell of the system to know which mode that is to be used in a certain situation or at a certain point in time. This is especially true for so called Random Access procedures, i.e. a procedure which is used by a user in a cell of the system when the user does not have a dedicated channel to the controlling node of the cell. A user may have a variety of devices by means of which he communicates with the system, examples of such devices being cellular telephones and portable computers. In the continued description, the generic term “user terminal” will also be employed.
Another factor which underlines the importance for the user terminals in a cell to know which multi antenna transmission mode that is to be used during, for example, the so called Random Access (RA) procedure, is the fact that many kinds of user terminals are equipped with multiple antennas, a trend which will probably increase in the future. If multiple antennas in the user terminal are to be used in the fashion demanded by the multi antenna transmission mode which is used by the eNodeB (or a corresponding node) in the cell, it is of course important for the user terminals to be aware of which mode it is that is in use at present, or that is to be used either in a certain situation.